Well, if your colon and kidneys are sufficiently clean then the flush should not have any serious repercussions. At the most, you will feel tired from the evening of day 6 to the evening of day 7, because of the body digesting the Epsom Salts which can be quite a load, apparently, and then because of the diarrhea on the morning and mid-day of day 7.
If your colon is not clean enough, you will absorb toxins back into your bloodstream, causing anything from aches, skin rashes, fatigue, to a worsening of the symptoms you already have.
If your kidneys are not clean enough, you will feel very tired and sluggish.
For a colon cleanse, I'd suggest that you do at least two 2 quartwater enemas before the flush, on day 6, and then 2 more on day 7 or 8. This is the least you can do and many people get by with just this.
Ideally, you should have done a more thorough Colon Cleanse by taking colosan for a fortnight or so before beginning to flush, or having done a colonic before every flush for the first 10 flushes at least. I did both, more or less.
Andreas Moritz recommends a colonic before and after every flush, but I find that is too much for the body to take and also very expensive. From an ayurvedic perspective, that amount of water being flushed up and down your intestines will dry them up and make them incapable of proper functioning.
For a kidney cleanse, take the herbal mix that Andreas recommends, which you can buy from the website present moment. Or take chanca piedra. I've done both. Do this once every 4 flushes or so.
Since you ask these questions, my guess is that you are yet to do a thorough review of the posts on this website - both the Liver Flush Forum and the liver Flush FAQ s, and also haven't gone through Andreas's book on the liver flush. If this is true, please do both things before you begin flushing.
Working with your internal organs to bring out toxins from them is no light matter, you should know what you are doing and be ready to be responsible for both the successes and failures. IT is a step towards being your own doctor, usually something people do after professional doctors have failed them. It is best to wait a few weeks before you are fully informed.